Laminated iron core induction corner-heating unit

ABSTRACT

An induction heating unit for the corners of an elongated workpiece of rectangular cross section. The unit has a core formed of iron laminations, and preferably has occasional copper laminations interspersed with the iron laminations. Each lamination has a pair of windows which define a central leg and webs between the window and workpiece. A winding of copper tubing extends around the leg within the windows. The webs form an unbroken wall protecting the winding from exposure to the workpiece.

United States Patent Emerson [4 Ma 16 1972 [541 LAMINATED IRON CORE INDUCTION 2,664,541 12/1953 Henderson ..336/2 14 x CORNER-HEATING UNIT 2,902,572 9/ l 959 Lackner et a] 2,832,877 4/1958 Dreyfus 219/1069 X [72] Inventor: William A. Emerson, Elhcott City, Md. [73] Assignee: United States Steel Corporation m Miner ASSISIGII! Examiner-B. A. Reynolds [22] Filed: June 10, 1971 Attorney-Walter P. Wood [21] Appl. No.: 151,667 ABSTRACT [52] Us Cl 219/10 43 219/1061 219/1069 An induction heating unit for the corners of an elongated 219/10 3 2 workpiece of rectangular cross section. The unit has a core [51] Int Cl liOSb 5/00 formed of iron laminations, and preferably has occasional Field 69 l O 79 copper laminations interspersed with the iron laminations. i i Each lamination has a pair of windows which define a central leg and webs between the window and workpiece. A winding of copper tubing extends around the leg within the windows. [56] References Cited The webs form an unbroken wall protecting the winding from UNITED STATES PATENTS exposure to the workpiece- 3,562,470 2/1971 Bobart ..2 1 9/ 10.43 6 Claims, 2 Drawing Figures 5 If /2 /3 W /0 v F /0@ Patented May 16, 1972 FIG.

FIG. 2.

/NVENT OR WILL/AM A. EMERSON y MMZ/ fl j A! rorney LAMINATED IRON CORE INDUCTION CORNER- I-IEATING UNIT This invention relates to an improved laminated iron-core induction heating unit for the corners of elongated workpieces of rectangular cross section.

Although my invention is not thus limited, my heating unit is particularly useful when embodied in a continuous-casting installation. Conventional practice in continuous casting is to pour liquid metal through an open-ended water-cooled mold. A casting of indefinite length emerges continuously from the lower end of the mold and usually travels through bending and straightening rolls which change its direction of movement to horizontal. As the casting leaves the mold, it has a liquid metal core surrounded by only a thin skin of solidified metal. To promote solidification of the core, intense water sprays are applied to the surface of the casting through a secondary cooling zone which starts immediately beneath the mold and may extend even beyond the straightening rolls.

By the time the casting has solidified throughout, its surface cools to a temperature too low for hot-rolling, for example to about l,200 to 1,500 F. Accordingly, if in-line rolling is practiced, the casting installation includes a reheating means through which the casting travels ahead of the roll stands. The reheating means must raise the surface temperature of the casting quite uniformly to a predetermined value which commonly lies with extremes of about 2,000 to 2,500" F. Both gas-fired furnaces and induction heating means have been used for this purpose.

There is a problem, which is more serious where induction heating is employed, that it is difficult to heat the comers of the casting to the same temperature as the faces with the uniformity required for the rolling operation. The faces may be heated satisfactorily by passing the casting through one or more conventional tunnel coils, but the corners remain too cool. This difficulty has been overcome by adding supplemental corner-heating units which have laminated iron cores, as shown in my joint patent with George F. Bobart, U.S. Pat. No. 3,562,470, and in our joint application Ser. No. 1 13,255 filed Feb. 8, I97 I. The unit of the present invention may be used to particular advantage as the corner heater in the arrangement shown in said patent and application. Nevertheless the unit may be used elsewhere, for example, in installations which do not include another heating means, or in which the workpieces are discrete lengths.

An object of my invention is to provide an improved laminated iron-core heating unit in which the core fully protects the windings against heat and scale from a workpiece.

A further object is to provide an improved unit of the foregoing construction in which the core has windows accommodating the windings and webs fully enclosing the windings.

A further object is to provide a unit of the foregoing construction which embodies improved water-cooling means for the core.

In the drawings:

FIG. 1 is a partially diagrammatic vertical sectional view taken between laminations of an induction heating unit constructed in accordance with my invention; and

FIG. 2 is a similar view showing a modification.

FIG. 1 shows left and right laminations 10 and 10a, a plurality of which are stacked in face-to-face relation to form two mating halves of a core in similar fashion to that shown in the aforementioned patent. Most of the laminations are iron, but preferably I intersperse occasional copper laminations, for example every sixth, as hereinafter explained. Although illustrated as right and left, the two halves may be upper and lower. Since the two halves are alike, but of opposite hand, I describe only the left half. Each left lamination 10 has a cutout 12 at its inner edge facing the right lamination 10a. The cutouts define a passage to accommodate an elongated workpiece W of rectangular cross section as it travels relatively to the unit. Each lamination has pole pieces 13 and 14 which protrude toward the workpiece at the top and bottom of the cutout l2.

In accordance with my invention, each lamination 10 has a pair of windows 15 and 16 which define a central leg 17 and integral webs 18 and 19 at the edges facing the workpiece W. I wind a suitable number of turns of electrically conductive tubing 22 (usually copper) around leg 17. The turns of the winding are insulated from one another and from the leg and are water-cooled in the usual fashion. The spaces around the turns may be filled with suitable insulation material such as an epoxy resin. The inner edges of the laminations carry a centrally located countersunk tube 23 welded to the laminations for circulating cooling water.

FIG. 2 shows a modification in which the countersunk tube 23 is replaced by a tube 24 welded to the edges of laminations l0 and protruding into the cutout 12. In this modification the tube 24 serves as a guide for the workpiece W, as well as for circulating cooling water. The core may also carry an external water-cooling tube 25 welded thereto. in other respects the modification is similar to the embodiment shown in FIG. 1; hence I have not repeated the description.

In operation, my heating unit serves to heat the corners of the workpiece W as described in the aforementioned patent. The webs 18 form an unbroken wall which fully encloses the winding 24 and thus fully protects the winding from heat and scale of the workpiece. In the example of continuous casting, a major portion of the workpiece already may be at a temperature of 2,000 F or higher when it passes through the cornerheating unit. The webs are comparatively thin (on the order of one-fourth inch). Hence they shunt only a relatively small fraction of the total flux before they become saturated, whereupon the windows act as though they were open slots. Since the webs themselves are exposed to high temperatures, it is necessary to remove heat from the core face through tube 23 or 24. The interspersed copper laminations also assist in removing heat from the core face, since they increase the heat conductivity of the core.

From the foregoing description, it is seen that my invention affords an induction heating unit of simple construction which overcomes difficulties encountered with the unit shown in the aforesaid patent. In that unit the windings are covered with plates bolted to the laminations, leaving open spaces along each edge. Scale may accumulate in these spaces and cause arc-overs and failures.

I claim:

1. In an induction heating unit for the corners of an elongated workpiece of rectangular cross section, which unit includes a core formed of iron laminations and a winding formed of turns of water-cooled electrically conductive tubing, said laminations having cutouts defining a passage to accommodate a workpiece traveling relatively to the unit, the combination therewith of an improved construction to protect said winding from exposure to the workpiece, each of said laminations having a pair of windows defining a central leg and integral webs, the tubing which forms said winding being wound within said windows around said leg, said webs lying between said winding and said passage and forming an unbroken wall therebetween.

2. A combination as defined in claim 1 comprising in addition occasional copper laminations interspersed with said iron laminations.

3. A combination as defined in claim 1 comprising in addition a tube fixed to the inside edges of said laminations for circulating cooling water.

4. A combination as defined in claim 3 in which said tube is countersunk.

5. A combination as defined in claim 3 in which said tube protrudes into said passage and serves also to guide the workpiece.

6. A combination as defined in claim 1 in which said core includes mating halves each of similar construction but of opposite hand. 

2. A combination as defined in claim 1 comprising in addition occasional copper laminations interspersed with said iron laminations.
 3. A combination as defined in claim 1 comprising in addition a tube fixed to the inside edges of said laminations for circulating cooling water.
 4. A combination as defined in claim 3 in which said tube is countersunk.
 5. A combination as defined in claim 3 in which said tube protrudes into said passage and serves also to guide the workpiece.
 6. A combination as defined in claim 1 in which said core includes mating halves each of similar construction but of opposite hand. 